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Sorry, Mr. pizza ...Sorry, Mr. pizza ...Posted Apr 15, 2008 6:36 UTC (Tue) by bronson (subscriber, #4806)In reply to: Sorry, Mr. pizza ... by JoeBuck Parent article: My kid hates Linux (ZDNet)
If 64 bit pointers are really that big a deal, how come the EDA guys don't use 4GB memory pools with 32-bit offsets? That's way you get the speed and huge memory space of 64 bits with the space efficiency of 32 bit. Seems like a win-win. It's been quite a while since I've done EDA (some VLSI layout and simulation back in 2003). I remember some seriously crufty software produced by vendors who would do anything to avoid an update. Some of the tools I used were written *and compiled* pre-1998! It was a nightmare trying to get that junk to run. I eventually got the toolchain working and then I never let anybody touch that box again. Not so much as a security update or a package upgrade lest it break anything. So... If the EDA industry is indeed pushing back against 64 bit, there might be more to it than just pointer size inflating the working set. :)
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Sorry, Mr. pizza ... Posted Apr 17, 2008 20:34 UTC (Thu) by jzbiciak (✭ supporter ✭, #5246) [Link] If 64 bit pointers are really that big a deal, how come the EDA guys don't use 4GB memory pools with 32-bit offsets? That's way you get the speed and huge memory space of 64 bits with the space efficiency of 32 bit. Seems like a win-win. Sounds like a maintenance nightmare to me, particularly if the code base is shared between 32-bit and 64-bit worlds, and if any portion of the data set has an index larger than 232-1. The reason I say "index" is that these pools could be homogeneous pools of structures, and so the addressed memory in that pool could actually be as large as 232 * sizeof(struct whatever), rather than just 232 bytes. Sure, on 64-bit machines you get the compact representation. But, on all machines that share that code base, you add an additional indirection to compute your final pointer, and you've thrown up partitions in your memory map based on where these pools are. If your problem doesn't partition into pools nicely, you're hosed.
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